In the field of drug delivery, it is recognized that supplying the drug in a correct temporal pattern is an important attribute of any drug delivery methodology. Controlled release drug delivery systems are intended to improve the response to a drug and/or lessen side effects of a drug. The recurring interest in chronopharmacology demonstrates the fact that biological rhythms are an important aspect of clinical pharmacology and should be taken into account when evaluating drug delivery systems (Hrushesky, W., J. Cont. Rel. 19:363 (1992), Lemmer, B., Adv. Drug Del. Rev. 6:19 (1991), Youn, C. B. J. Cont. Rel. 98 (3) 337 (2004) and Youn, C. B. J., Ed., “Chronopharmaceutics,” John Wiley & Sons, New York (In preparation)).
The onset and symptoms of diseases such as asthma attacks, coronary infarction, angina pectoris, stroke and ventricular tachycardia are circadian phase dependent. In humans, variations during the 24 h day in pharmacokinetics (chrono-pharmacokinetics) have been shown for cardiovascular active drugs (propranolol, nifedipine, verapamil, enalapril, isosorbide 5-mononitrate and digoxin), anti-asthmatics (theophylline and terbutaline), anticancer drugs, psychotropics, analgesics, local anesthetics and antibiotics, to mention but a few. Even more drugs have been shown to display significant variations in their effects throughout the day (chronopharmacodynamics and chronotoxicology) even after chronic application or constant infusion (Ohdo, S. Drug Safety 26 (14) 999-1010 (2003)). Moreover, there is clear evidence that dose/concentration-response relationships can be significantly modified based on the time of day. Thus, circadian time has to be taken into account as an important variable influencing a drug's pharmacokinetics and its effects or side-effects (Bruguerolle, B., Clin. Pharmacokinet. Aug. 35 (2) 83-94 (1998)).
Studies indicate that the onset of certain diseases show strong circadian temporal dependency. This has led to the need for timed patterning of drug delivery as opposed to constant drug release (Lemmer B., Ciba Found Symp. 183:235-47; discussion 247-53 (1995).
The term “controlled release” refers generally to delivery mechanisms that make an active ingredient available to the biological system of a host in a manner that supplies the drug according to a desired temporal pattern. Controlled release drug delivery systems may be implemented using: a) instantaneous release systems; b) delayed release systems, and c) sustained release systems. In most cases, controlled release systems are designed to maintain a sustained plasma level of an active ingredient in a drug within a human or animal host over a period of time.
Instantaneous release refers to systems that make the active ingredient available immediately after administration to the biosystem of the host. Instantaneous release systems include continuous or pulsed intravenous infusion or injections. Such systems provide a great deal of control because administration can be both instantaneously started and stopped and the delivery rate can be controlled with great precision. However, the administration is undesirably invasive as they involve administration via a puncture needle or catheter.
Delayed release refers to systems in which the active ingredient made available to the host at some time after administration. Such systems include oral as well as injectable drugs in which the active ingredient is coated or en-capsulated with a substance that dissolves at a known rate so as to release the active ingredient after the delay. Unfortunately, it is often difficult to control the degradation of the coating or encapsulant after administration and the actual performance will vary from patient to patient.
Sustained Release generally refers to release of active ingredient such that the level of active ingredient available to the host is maintained at some level over a period of time. Like delayed release systems, sustained release systems are difficult to control and exhibit variability from patient to patient. Due to the adsorption through the gastrointestinal tract, drug concentrations rise quickly in the body when taking a pill, but the decrease is dependent on excretion and metabolism, which cannot be controlled. In addition, the adsorption through the gastrointestinal tract in many cases leads to considerable side effects (such as ulcers), and can severely damage the liver.
Transdermal therapeutic systems (TTS) have been developed primarily for sustained release of drugs in situations where oral sustained release systems are inadequate. In some cases, drugs cannot be effectively administered orally because the active ingredients are destroyed or altered by the gastrointestinal system. In other cases the drug may be physically or chemically incompatible with the coatings and/or chelating agents used to implement sustained release. In other cases a transdermal delivery system may provide sustained release over a period of days or weeks whereas orally administered drugs may offer sustained performance over only a few hours. A wide variety of active substances can be delivered through transdermal systems so long as the active substance can be provided in a form that can cross the skin barrier, see for example, U.S. Pat. No. 6,638,528, which is incorporated herein by reference.
In most cases transdermal delivery systems are passive, taking the form of a patch that is attached to the skin by an adhesive. The TTS includes a quantity of the active substance, along with a suitable carrier if need be, in a reservoir, matrix or in the adhesive itself. Once applied, the active ingredient diffuses through the skin at a rate determined by the concentration of the active substance and the diffusivity of the active substance. However, a variety of physical and chemical processes at the skin/patch boundary affect the delivery rate and may eventually inhibit drug delivery altogether.
The original performance target for controlled drug delivery is to achieve a zero-order release rate of the drug, so that a constant efficacious drug concentration is maintained in the blood plasma. However, more than two decades of research in chronobiology and chronopharmacology have demonstrated the importance of biological rhythms to the dosing of medications as well as determine the influence of a patient's circadian or other biological rhythms on drug efficacy and efficiency. This research reveals that certain disease symptoms follow a daily pattern, with peak symptoms at certain times of the day. It has been widely acknowledged that hormones, neurotransmitters and other intra-body compounds are released in different amounts at different times of the day pursuant to daily patterns.
The new approach stems from a growing body of research that demonstrates that certain diseases tend to get worse at certain times of the day. By synchronizing medications with a patient's body clock, many physicians believe that the drugs will work more effectively and with fewer side effects. In some cases, the improvements have been so pronounced that doctors have been able to reduce dosages. Circadian physiologic processes have been found to alter drug absorption, distribution, metabolism, and excretion. As a result, drug doses need to be adjusted to meet the differing needs of target organs or tissues at various times of the day (see, L. Lamberg, American Pharmacy, N831 (11): 20-23 (1991)).
The continued interest in chronopharmacology shows the ever-increasing need to develop technologies to control the temporal profile in drug delivery. Research findings suggest that the onset and severity of many diseases are cyclic in nature, or follow circadian patterns. Drug tolerance adds to the need for modulation of drug dosing profiles. Additionally, skin irritation and sensitization caused by medications may require intervals during which no drug is administered. Therefore, this improved form of drug delivery will be very important to people who need medicine easily, painlessly and automatically delivered to their bodies in timed increments (see Smolensk, M. H. & Lamberg, L. Body Clock Guide to Better Health: How to Use Your Body's Natural Clock to Fight Illness and Achieve Maximum Health, Henry Holt & Company, New York (2001) and Grimes, J. et al., J Pharmacol Exp Ther 285 (2): 457-463 (1998)).
Active transdermal delivery systems have been developed to help regulate the delivery rate by providing mechanisms to improve drug delivery over time by “pumping” the active ingredient. One such system, (U.S. Pat. No. 5,370,635), describes a system for delivering a medicament and dispensing it to an organism for a relatively long period of time, for example at least a few days. The device can be adapted for positioning on the surface of the skin of a human or possibly an animal body in order to apply a medicament thereto from the outer side thereof. Conventional transdermal systems circumvent the disadvantages of the adsorption through the gastrointestinal tract, but they do not optimize or tailor the dosing regiment to offset peak symptoms. In addition the constant transdermal delivery of a drug can lead to severe side effects, including debilitating sleep disorders and ever increasing tolerance.
A simple type of transdermal chronotherapy is a biphasic profile, in which the drug concentration changes from a high to a low level (or vice versa) over time. Although the system can be physically applied or removed to alter the drug level, patient compliance with this procedure may be difficult, particularly during inconvenient hours. To generate a biphasic profile, the delivery system may utilize an external regulator, as described in Fallon et al. (U.S. Pat. No. 5,352,456, 1994) which illustrates a device for drug administration through intact skin that provides an initial pulse in the flux of the drug through the skin followed by a substantially lower flux of drug through the skin. Additionally, Fallon et al. (U.S. Pat. No. 5,820,875, 1998) later describe a device for the administration of a drug through an area of intact skin over a period of time in which the flux of the drug through the skin varies temporally in a controlled manner. The device is such that the skin flux of the drug varies in a controlled manner over the period of administration, typically from a high flux in the initial stage of administration to a lower flux in the later stage of administration.
Transdermal temporally controlled drug delivery systems, proposed by Giannos et al. (U.S. Pat. No. 6,068,853, 2000) coupled pH oscillators with membrane diffusion in order to generate a periodic release of a drug or active ingredient transdermally, without external power sources and/or electronic controllers. The intent was to address chronotherapy with a pulsatile transdermal system. The strategy was based on the observation that a drug may be rendered charged or uncharged relative to its pKa value. Since only the uncharged form of a drug can permeate across lipophilic membranes, including the skin, a periodic delivery profile may be obtained by oscillating the pH of the drug solution (see Giannos, S. A., “Pulsatile Delivery of Drugs and Topical Actives,” in “Novel Topical Actives and Delivery Systems: Cosmetics, Dermatologicals and Transdermals”, Edited by John. J. Wille, Jr.: Blackwell Publishing, Oxford UK (In press)).
Recently, an orally administered drug for arthritis treatment has suggested a chronotherapeutic approach using a delay release system. The delay is scheduled to release the active ingredient at the beginning of an interleukin 6 cascade that is believed to cause early morning stiffness in rheumatoid arthritis patients. By attempting to synchronize the drug delivery with a biological cycle it is believed that low doses may be used to achieve desired results. However, this system does not overcome the limitations of delayed release systems described above.
Although it is possible to meet the requirements of chronopharmacology with pills, this requires an enormous amount of discipline by the patient to comply with the treatment regiment, see for example, U.S. Pat. No. 6,214,379, which is incorporated herein by reference. As illustrated earlier, to achieve optimal results, many patients may need to wake up during the night to take their medication. Hence, what is needed is a non-invasive, reliable means of delivering drugs compounds in precisely timed and measured doses-without the inconvenience and hazard of injection, yet with improved performance as compared to orally delivered drugs.
Addressing patient compliance (taking the proper dosages at the prescribed times) is another critical problem facing caregivers and pharmaceutical firms alike. Studies show that only about half of patients take medications at the times and in the dosages directed by their physician. It is reported that each year, 125,000 deaths and up to 20% of all hospital and nursing home admissions result from patient noncompliance. It is estimated that non-compliance results in additional healthcare costs in excess of $100 billion per year in United States. These figures are even more pronounced for the elderly.
An individual's failure to comply with a dosing regimen, e.g. failure to take one or more doses of a drug or taking too many doses, will have an adverse impact upon the success of the regimen. Individuals may fail to comply with their drug dosing regimen for a number of reasons. For example, drug dosing regimens, such as every 4 hours, i.e., 8-12-4-8 involve a rigid dosing schedule that may be incompatible with an individual's personal schedule. Such a rigid dosing schedule when combined with normal human traits such as forgetfulness or denial of a medical condition, as well as a busy life, represent substantial obstacles to compliance with a drug dosing regimen. Accordingly, such rigid dosing regimens often result in the failure by an individual to take one or more doses at the prescribed time. This has an adverse impact on the levels of the therapeutic substance at the active site and consequently on the overall efficacy of the therapeutic substance. Hence, a need exists for systems and methods that increase patient compliance for administration of a variety of drugs.
Additional advantages and novel features of this invention shall be set forth in part in the description that follows, and in part will become apparent to those skilled in the art upon examination of the following specification or may be learned by the practice of the invention. The advantages of the invention may be realized and attained by means of the instrumentalities, combinations, compositions, and methods particularly pointed out in the appended claims.